Nanocrystalline Gadolinium-Doped Hydroxyapatite: Synthesis, Characterization and Cytotoxicity Assessment for Enhanced Drug Delivery Applications

Hydroxyapatite (HAp) is a ceramic material predominantly composed of calcium phosphate, possessing a crystalline structure similar to natural human bone. It holds a wide range of applications in the medical field, such as dental implants, and serving as a bone filler in orthopedic surgery. Moreover, HAp can be enriched with rare earth elements to bestow its luminescent properties. This makes HAp-based nanocarriers ideal candidates for incorporation into polymeric nanoparticles, which can be designed as nanospheres or nanocapsules, functioning as channels for precise drug delivery within biological systems.<br/>In this study, we synthesized gadolinium-doped HAp nanofibers (HAp-Gd) using the Microwave-Assisted Hydrothermal Method to evaluate their suitability as drug carriers. After this, the HAp-Gd samples were characterized through X-ray diffraction. HAp-Gd was identified by comparing the results with the ICDD PDF files provided by Bruker. Morphological analysis and the determination of the elemental chemical composition of HAp-Gd nanofibers were performed through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy. Subsequently, luminescence analyses were executed to examine the interaction between the drug intended for transportation and the HAp-Gd nanostructures. This assessment was performed by analyzing the samples using photoluminescence spectroscopy. Then, we conducted an AlamarBlue Assay to assess the biosecurity and cytotoxicity of HAp-Gd in a culture model of chicken embryo fibroblasts. Results obtained from X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy collectively demonstrated the exceptional characteristics of the synthesized HAp nanofibers. These characteristics include a high level of crystallinity, purity, a hexagonal morphology, and a preferential crystalline orientation.<br/>Furthermore, the chemical composition was uniform, indicating excellent integration of gadolinium into the HAp structure. Additionally, the biomaterial exhibited notable photoluminescent properties, suggesting its potential as a facilitator for drug transport within biological systems. Also, the results of the AlamarBlue assay indicate that the HAp-Gd does not exert a cytotoxic effect on fibroblasts.<br/>In conclusion, the microwave-assisted Hydrothermal Method proved highly effective in synthesizing gadolinium-doped hydroxyapatite nanofibers with unique morphological and structural characteristics. We also demonstrate that this material is safe at the cellular level. These findings reinforce its potential application as a secure drug carrier in biological systems.